Traditional structures and products experience deterioration or failures of various kinds which create a need for reinforcement. For example, roadways consisting of asphaltic concrete materials experience deterioration and failure over time in the form of reflective cracking, rutting, rolling up at traffic lights and "potholes". This deterioration and failure of asphaltic concrete roadways require costly, frequent, and time consuming repairs. Another family of products, concrete structures, such as columns, flat slabs, or constant cross-section shapes, deteriorate over time or as a result of seismic activity or need reinforcement for improved properties such as tensile strength. Various approaches have been investigated to address these problems by reinforcing the initial or existing products.
In regards to roadways, asphalt roadways are widely used, yet experience frequent and costly types of deterioration. Asphalt paving consists of an asphalt compound combined with "rock aggregate". The aggregate adds to the compression strength of the asphalt with the asphalt compound acting as a matrix to bind the road together. Asphalt roads deteriorate more quickly than concrete roads, and typical forms of deterioration are "reflective cracking", curling of the asphalt at places like stoplights, grooving of the asphalt due to repeated vehicular traffic following the same path down the roadway and other cracking of the asphalt surface. "Reflective cracking" is a major problem in asphalt overlays of existing concrete roads or other road foundations. Reflective cracking occurs where cracks in the existing concrete or asphaltic road or foundation propagate from the existing road up through the new asphalt overlay. This requires costly repairs to otherwise new roads and attacks the strength of the new overlay.
A variety of materials have been tried in the past to attempt to provide reinforcement or stabilization for asphalt roadways. Several products currently seek to address the reflective cracking problem. One product is a non-woven overlay fabric or mat between a concrete road and an asphalt overlay called Petromat.RTM. from Amoco Fabrics and Fibers. Petromat.RTM. uses a random orientation of polypropylene fibers in a fabric mat that is laid down as a barrier between a road or road foundation and an asphalt overlay. The polypropylene does not have the modulus to resist expansion of concrete road in attempting to address the problem of reflective cracking. Also, the mat is of tight construction and does not allow asphalt or concrete to pass through the structure, instead acting as a barrier between the layers. The mat is therefore not incorporated as a reinforcement structure throughout the new overlay. Instead, the mat acts only as a barrier which can wrinkle or fold in application. Further, a leveling or filling of cracks is necessary before using the Petromat .RTM..
Others have tried to use mesh structures of plastic materials and woven fabrics to reinforce roadways. One product, Glasgrid.RTM. is a woven (leno) glass fiber fabric grid, coated with asphalt black coating with one side having self-adhesive properties. Another product, Raupave.RTM. is a geogrid composed of high-tenacity fiberglass yarn which is woven into a uniform, leno grid configuration. Another product, Polyfelt PGM-G.RTM. consists of fiberglass rovings laid in a grid pattern onto a non-woven felt with the felt meant to act as a water barrier to attempt to retard reflective cracking.
Attempts have been made to use other tightly constructed structures which reinforce the roadway, but do not allow the passage of asphaltic concrete road materials through the reinforcing structure in the normal paving process. Difficulties have arisen from using such tightly constructed reinforcement members in road construction. These tightly constructed reinforcement members create a barrier between the new road overlay and the old road or foundation restricting the passage through or incorporation of asphaltic concrete materials into the reinforcement member. This reduces the reinforcement benefits of the reinforcing member and enables slippage or movement in the normal paving process.
Another family of products and structures which require reinforcement are concrete structures and other masonry or cementitious materials. These concrete materials have low tensile strength yet have good compressive strength. When using concrete as a structural member, for example, in a bridge, building or the like, reinforcement is often used to impart the necessary tensile strength. In new and existing concrete structures, such as precast driveways, slabs, sidewalks, pipe etc, reinforcement has been undertaken with a variety of steel shapes such as open steel meshes, steel rebar, and steel grids. Steel grids have been used in reinforcing concrete structures such as decking for drawbridges. These steel grids are a closed cell structure, and each section of steel grid contains and confines a rectangular or square column of concrete. These types of grids are inherently very inefficient in their use of the reinforcing material.
Steel and other metals used as a reinforcing agent are subject to corrosion. The products of corrosion result in an expansion of the column of the steel which causes a "spalling" effect which can cause a breakup and deterioration of the concrete structure. This breaking and crumbling of concrete structures are severe in areas of high humidity and areas where salt is used frequently on roads, driveways and sidewalks to melt ice or snow. Bridges over waterways in areas such as the Florida coast or Florida Keys are exposed to ocean air which causes deterioration and a short lifespan requiring constant rebuilding of these bridges. Concrete structures in the Middle East use concrete made with the local acidic sand which also causes corrosion of steel reinforcements.
To replace traditional steel in reinforcing concrete, many types of plastics have been considered. One attempted replacement for steel in reinforcement uses steel rebars coated with epoxy resin. Complete coating coverage of the steel with epoxy, however, is difficult. Also, due to the harsh handling conditions in the field, the surface of the epoxy coated steel rebars frequently will be nicked. This nicking results in the promotion of localized, aggressive corrosion of the steel and results in the same problems as described above.
Fiberglass composite rebars have been used in reinforcing concrete structures such as the walls and floors of x-ray rooms in hospitals where metallic forms of reinforcement are not permitted. The method of use is similar to steel rebars. The fiberglass composite rebars have longitudinal discrete forms which are configured into matrixes using manual labor. Concrete is then poured onto this matrix structure arrangement.
Fiberglass composite rebars are similar to steel rebars in that the surface is deformed. Fiberglass gratings which are similar to steel walkway gratings also have been used as reinforcements in concretes, but their construction, which forms solid walls, does not allow the free movement of matrix material. This is due to the fact that the "Z" axis or vertical axis reinforcements form solid walls.
In dealing with reinforcing concrete support columns or structures, wraps have been applied around the columns to act like girdles and prevent the concrete from expanding and crumbling. Concrete is not a ductile material, thus, this type of reinforcing is for only the external portion of the column. One type of wrap consists of wrapping a fabric impregnated with a liquid thermosetting resin around the columns. The typical construction of these wraps has glass fiber in the hoop direction of the column and glass and Kevlar fibers in the column length direction. Another approach uses carbon fiber uni-directional (hoop direction) impregnated strips or strands which are designed to be wound under tension around deteriorated columns. The resulting composite is cured in place using an external heat source. In these approaches the materials used in the reinforcing wraps are essentially applied to the concrete column in an uncured state, although a prepreg substrate may be employed which is in a "semi-cured" state, i.e. cured to the B-stage. When using a woven fabric, "kinking" can take place when using either carbon or glass fibers, because the weaving process induces inherent "kinks" in either a woven wet laminate or woven prepreg, which results in a less than perfectly straight fiber being wrapped around the column.
Another approach to reinforcing concrete structures and columns is to weld steel plates around the concrete columns to give support to the concrete wall. Such steel plates are also subject to corrosion and loosening resulting from deterioration of the column being supported. This approach is only an external reinforcement and lacks an acceptable aesthetic appearance which makes it undesirable.
An approach to reinforcing concrete mixes has been using short (1/4 to 1") steel, nylon or polypropylene fibers. Bare "E-type" glass fibers are generally not used due to the susceptibility of glass fibers to alkaline attack in Portland cement.
Thus, there is a need for improved structural members adapted to reinforce a variety of products. For example, there is a need for an improved structural reinforcement member for use in asphaltic concrete roadways. Additionally, there continues to be a need for a structural reinforcement member for concrete structures which accomplishes the reinforcement or increases material properties of the concrete structure without being subject to corrosion or attack. There also remains a need for methods to reinforce products using these structural members.
It is an object of the invention to overcome the deficiencies of the prior art as noted. A more particular object of this invention is to provide a structural member adapted to effectively reinforce a variety of different products. A further object of the invention is to provide methods for utilizing the structural member adapted to reinforce a product, and for efficiently producing the structural member.